Bushing

ABSTRACT

A bushing utilizes a fabric reinforced thermoset composite sleeve incorporated within an outer shell in a construction enabling the sleeve to be press-fitted within the shell and held therein by a constriction in the shell bore which is embraced by the bearing liner. Following installation of the bearing sleeve, the sleeve bore may be reamed to provide a uniform inside diameter.

BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention relates to industrial and commercial bushings for use ina wide variety of applications.

There is a continuing need for a lightweight, low-cost, self-lubricatingbushing for use in industrial and commercial applications. Bushingshaving a self-lubricating bearing sleeve made from a fabric reinforcedthermoset composite could be of substantial use if there were a low-costsimple way of assembling such fabric reinforced thermoset compositewithin a bushing shell.

2. Background Art

U.S. patents showing bushings over which my disclosure represents animprovement are as follows:

-   -   U.S. Pat. No. 5,685,057    -   U.S. Pat. No. 3,945,695    -   U.S. Pat. No. 4,740,117

A publication entitled “General Engineering Manual” by Orkot Ltd. ofBradmarsh Business Park, Rotherham, S60 1 BX, South Yorkshire, England,also shows prior art information.

SUMMARY OF THE INVENTION

I have discovered that a fabric reinforced thermoset composite sleevemay be incorporated within an outer shell of a bushing in a constructionwhich enables the sleeve to be press-fitted within the shell to be heldtherein by a constriction in the shell bore which is embraced by thebearing liner. As the inner bearing sleeve or liner is pressed axiallyinto the shell, it encounters the constriction which is shaped to permitthe sleeve to be squeezed past it. Because the sleeve is distorted atthe constriction, the sleeve bore is reamed or otherwise sized afterinstallation of the sleeve to provide a uniform internal diameterthroughout the sleeve. The constriction of the shell is greater than therunning clearance between the inside diameter of the sleeve and theoutside diameter of the shaft or pin carried by the bushing, such thatthe sleeve cannot work its way out of the bushing once the shaft is inplace during operation thereof.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view of a bushing embodying my invention;

FIG. 2 is a perspective exploded view of a bearing sleeve to bepress-fitted into the bearing shell;

FIG. 3 is a view partially in section through a bushing embodying theinvention;

FIG. 4 is a fragmentary view taken at the circle 4 in FIG. 3; and

FIG. 5 is a view partially in section through a slightly differentexternal configuration of the bushing.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT(S)

As shown in the drawings, the bushing comprises an outer shell, orbushing shell 10, and an inner bearing sleeve 12, both of generallycylindrical configuration. The bearing sleeve 12 is press-fitted withinthe shell 10.

The shell 10 has an inner cylindrical surface 14 of constant diameterexcept for the interruption by a radially, inwardly displaced wallportion or constriction 16, best shown in FIG. 4. While only one suchconstriction is shown, it is to be understood that multiple, axiallyspaced apart constrictions may be provided if desired. The constriction16 preferably extends 360° around the cylindrical bore and its inwarddisplacement exceeds the running clearance (RC) between the shaft 18 tobe carried by the bearing and the internal surface 20 of the bearingsleeve. For example, the inward displacement of the shell wall at theconstriction may be on the order of 0.008 inches, +0.00 inches and−0.002 inches. The RC will be somewhat less than this, for example,0.0005 to 0.001 of an inch (per side).

When the bearing sleeve 12 is pressed into the shell 10, the sleeveencounters the constriction 16 but the pressure forcing the bearingsleeve axially into the shell should be sufficient to cause the sleeveto squeeze through the constriction and abut the flange 22 at the end ofthe shell bore. As will be apparent from FIG. 3, the constriction 16 islocated substantially midway between opposite ends of the shell bore 14,though it may be placed at any other suitable or multiple locations.

The constriction 16 is preferably shaped to provide a smooth, hump-likecontinuous annular ring around the inside of the shell 10 such that thesleeve will be squeezed through the constriction. For this purpose, theconstriction has smoothly shaped portions 16 a and 16 b at each side ofthe nest. For example, in a bushing for a one-inch shaft the hump may beformed on approximately a radius R (see FIG. 4) of 0.20 inches with anoverall axial length L of 0.112 inches. Following the reaming theinternal diameter of the sleeve is uniform as there has been a reductionin wall thickness of the sleeve at the point where the sleeve overliesthe constriction.

The shell 10 may be formed of a pre-hardened steel or other metal and isrelatively rigid as compared with the liner 12. The constriction 16 maybe the result of an increased thickness wall section for the shell asshown in FIG. 4, or the shell may be inwardly upset at the location ofthe constriction to provide the reduced diameter portion.

The bearing sleeve 12 is preferably formed of a fabric reinforcedthermoset composite. One such composite which has been found suitable issold by Orkot Ltd. of Bradmarsh Business Park, Rotherham, S60 1 BX,South Yorkshire, England and specifically the product identified asLuytex C394. Also, a product sold under the mark “Lubricom” by PolygonCompany of Walkerton, Indiana may be satisfactory. The Luytex product isan Aramid fiber with a high temperature resin system and incorporatespolytetrafluoroethylene for lubrication purposes.

The liner 12 will give or flex slightly so that it will “wrap” around ashaft supported in the bushing such as the shaft 18 and thus increasethe bearing surface area between the shaft and the sleeve avoiding aline contact which can adversely affect bearing life. This flexing ofthe liner also enables it to be pressed through the constriction 16 asabove described.

In FIG. 5, I have shown a slight modification of the bushing in whichthe shell 24 is provided with an external flange 26 at one end asopposed to the flange 23 of the shell shown in FIG. 3. The constrictioncomprises a discontinuous ring of circumferentially spaced apart ringsegments 17. Such ring segments, each being enveloped by the sleeve 28,will prevent any tendency of the sleeve to rotate relative to the shellwhere a rotating shaft is received within the bushing as distinguishedfrom a reciprocating pin. I have found that for most applications thecontinuous ring constriction shown in FIG. 3 will prevent both axialrotational displacement between the sleeve and shell, but thediscontinuous segments 17 shown in FIG. 5, on occasion may be useful.

By having the constriction 16 or 17 greater than the running clearancebetween the shaft or pin 18 and the sleeve 12 or 28, with the shaft orpin in place, as during normal operation of the bearing, the sleeve willnot be able to move out of position as the thickness of the sleeve onopposite sides of the constriction will prevent such movement.

It will also be noted in FIG. 5 that the right hand end of the shell 24has a bull-nose shape defined by a circumferential chamfer 25 whichfacilitates insertion of a pin or shaft (not shown) into the right handend of the bushing.

While embodiments of the invention have been illustrated and described,it is not intended that these embodiments illustrate and describe allpossible forms of the invention. Rather, the words used in thespecification are words of description rather than limitation, and it isunderstood that various changes may be made without departing from thespirit and scope of the invention.

1. A bushing comprising, in combination: an outer shell having an innercylindrical surface interrupted by a radially inwardly displaced wallportion; an inner bearing sleeve disposed within the shell in apress-fit relationship and overlying the inwardly displaced wallportion; that portion of the inner bearing sleeve overlying the inwardlydisplaced wall portion being of a sufficiently reduced wall thickness toprovide a constant inside diameter for the inner bearing sleeve; and theinside diameter of the inner bearing sleeve sized to provide a smoothrunning fit between the inner sleeve and a shaft extending through andsupported in the bushing.
 2. The bushing of claim 1 wherein the radiallyinwardly displaced portion extends circumferentially around the insideof the outer shell.
 3. The bushing of claim 2 wherein said inwardlydisplaced portion comprises a discontinuous ring of circumferentiallyspaced apart ring segments.
 4. The bushing of claim 2 wherein saidinwardly displaced portion comprises a continuous circumferential ribprojecting radially inwardly from the cylindrical wall of the sleeve. 5.The bushing of claim 1 wherein the radially inward displacement of thewall portion of the shell is greater than the running clearance betweena shaft supported in the bearing and the inside diameter of the innersleeve.
 6. The bushing of claim 1 wherein the inner bearing sleeve isformed of a fiber reinforced plastic.
 7. The bushing of claim 1 whereinthe shell is relatively rigid and the inner sleeve is resilientlydeformable to squeeze over the inwardly displaced wall portion of theshell when the inner sleeve is pressed coaxially into the shell.
 8. Thebushing of claim 1 wherein the shell is relatively rigid and the innersleeve is resiliently deformable to squeeze over the inwardly displacedwall portion of the shell when the inner sleeve is pressed coaxiallyinto the shell.
 9. The method of making a bushing comprising: providinga relatively rigid shell having a cylindrical bore interrupted by aradially inwardly displaced wall portion forming a constriction in suchbore; providing a resilient bearing sleeve sized to be press fitted intosaid bore; pressing said sleeve axially into said sleeve bore and beyondsaid constriction and causing the sleeve to embrace the constriction;and reaming the sleeve bore to provide a uniform internal diameter.